Hydraulic Hammer

ABSTRACT

A piston cylinder is formed inside a ram and is fitted with a piston attached to a stationary hollow piston rod, creating a upper piston chamber for receiving pressurized hydraulic fluid, which causes the ram to rise as the volume of the upper piston chamber is expanded due to the hydraulic pressure and increasing volume of hydraulic fluid. When the ram reaches predetermined desired height, hydraulic pressure is released by opening a directional valve, allowing the ram to drop. A lower piston chamber is sealed and filled with gas. A moveable shuttle member that reciprocates up and down inside a hollow piston rod in response to the changing volume of the lower piston cylinder, facilitating the evacuation of hydraulic fluid from the upper piston chamber. An alternative embodiment uses a single fluid and has no shuttle member.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

SEQUENCE LISTING

Not applicable

BACKGROUND OF THE INVENTION

The present invention is related to an improved hydraulic hammer principally for driving piles into the earth.

DESCRIPTION OF THE RELATED ART INCLUDING INFORMATION DISCLOSED UNDER 37 C.F.R. 1.97 and 1.98

Many structures, including for example, buildings, piers and the like, are supported by piles that are driven into the ground, either dry ground or ground that is underwater.

Dropping a free weight of a certain weight from a certain height is one common technique for driving piles. An advantage of this technique is that the force needed to drive the pile further corresponds to the load the pile can bear in use and well-known tables allow builder to calculate the load bearing capacity very accurately. A disadvantage of this technique is that the weight must be raised a substantial height and the lifting mechanism, typically a crane, is even higher, requiring a good deal of space, or headroom, available above the pile. Another disadvantage of this technique is that it is typically relatively slow, reducing productivity.

Also frequently used for driving piles are hydraulic hammers. One hydraulic hammer is disclosed in U.S. Pat. No. 6,557,647, which describes a hammer having a piston cylinder inside a ram, with the stationary piston fixed to a stationary solid piston rod, which is fixed to the bottom of the ram. The piston forms an upper piston cylinder above the piston and a lower piston cylinder below the piston. Hydraulic fluid under pressure is forced into a lower piston chamber to raise the ram above the pile and hydraulic fluid under pressure is forced into the upper chamber as the ram fall toward the extended, or striking, position. A substantial physical portion of this device lies outside of the ram, increasing the headroom needed for its operation. The structure is also mechanically complex. It also requires several valves.

Therefore, there is a need for a low headroom hammer that is a hydraulic hammer.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide a nearly free-fall hydraulic hammer that has a faster cycle time than conventional hammers and, in some embodiments, to provide a low-headroom hydraulic hammer.

It is another object of the present invention to provide a hydraulic hammer that requires less energy to operate than similar conventional hammers.

It is another object of the present invention to provide a nearly free-fall low headroom hydraulic hammer that has a smaller overall weight than comparable hammers of similar impact.

It is another object of the present invention to provide a nearly free-fall low headroom hydraulic hammer that has a low headroom, permitting its use in situations where a hammer cannot be raised high above the pile to be driven, i.e., a low headroom environment.

It is another object of the present invention to provide a nearly free-fall low headroom hydraulic hammer that mimics the impact force of a true free-falling hammer or weight, which have very precise driving property tables for calculating pile load bearing factors, allowing the present hammer to utilize these well-developed load tables.

These and other objects of the invention are achieved by providing a nearly free-fall hydraulic hammer, which may be a low-headroom hydraulic hammer, in which a ram having a piston cylinder inside it is lifted by pumping hydraulic fluid into the chamber above a stationary piston and then dropping the ram by relieving the pressure on the hydraulic fluid. The low-headroom hydraulic hammer is made a relatively short and therefore, low headroom, hammer by having the cylinder and the piston located entirely inside the ram or actuator. A closed sealed compressed gas chamber in the piston cylinder below the piston and continuing up into a hollow piston rod provides a spring-like bounce to accelerate the outflow of the hydraulic fluid from the chamber above the piston. In one embodiment a sealed cylindrical shuttle member inside the hollow piston connecting rod reciprocates between an upper stop member and a lower stop member, to change the gas pressure inside the sealed gas chamber and also serves as a barrier between the hydraulic fluid and the gas, keeping them separated. In another embodiment, the shuttle member is omitted and only a single working fluid, a hydraulic fluid is used. In another embodiment a receptacle, resembling a bucket or other convenient shape, is connected to the bottom of the piston to old hydraulic fluid and thereby reduce the volume of hydraulic fluid that must be pumped, thereby reducing the cycling time for a give size hydraulic pump and increasing the efficiency of the hydraulic hammer. In all embodiments, the ram of the hammer moves between a first position, which is the ram at its maximum lift point above the pile, which is predetermined, and a second position, which is the lowest position of the ram, i.e., the striking position.

Other objects and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, the preferred embodiment of the present invention and the best mode currently known to the inventor for carrying out the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross section side view of a first embodiment of a hydraulic hammer (hammer) according to the present invention having a reciprocating shuttle member inside a hollow piston rod and showing the hammer at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle, that is, in a second position.

FIG. 2 is a cross section side view of the hammer of FIG. 1 at the beginning the hammer lifting stroke.

FIG. 3 is a cross section side view of the hammer of FIG. 1 shown at a position during the lifting stroke of the ram.

FIG. 4 is a cross section side view of the hammer of FIG. 1 shown at the top of its predetermined height and the beginning of the falling stroke of the ram, that is, in a first position.

FIG. 5 is a cross section side view of the hammer of FIG. 1 shown during the falling stroke of the ram.

FIG. 6 is a cross section side view of the hammer of FIG. 1 shown at the end of the falling stroke, having made impact with the pile or other driven object, at which point, the hammer is returned to the configuration of FIG. 1, in equilibrium, at rest and ready to begin another cycle.

FIG. 7 is a cross section taken along lines 7-7 of FIG. 1 or FIG. 8.

FIG. 8 is a cross section side view of another embodiment of a hydraulic hammer (hammer) according to the present invention showing the hammer at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle.

FIG. 9 is a cross section side view of the hammer of FIG. 8 at the beginning the hammer lifting stroke.

FIG. 10 is a cross section side view of the hammer of FIG. 8 shown at a position during the lifting stroke of the ram.

FIG. 11 is a cross section side view of the hammer of FIG. 8 shown at the top of its predetermined height and the beginning of the falling stroke of the ram.

FIG. 12 is a cross section side view of the hammer of FIG. 8 shown during the falling stroke of the ram.

FIG. 13 is a cross section side view of the hammer of FIG. 8 shown at the end of the falling stroke, having made impact with the pile or other driven object, at which point, the hammer is returned to the configuration of FIG. 8, in equilibrium, at rest and ready to begin another cycle.

FIG. 14 is a cross section side view of another embodiment hydraulic hammer, in which a cylinder having a closed lower end is attached to the lower surface of a piston, i.e., forming a receptacle resembling a bucket, suspended beneath the piston and reciprocating within a well below the otherwise normal floor of the piston cylinder to reduce the volume of fluid that must be removed from the cylinder space below the piston, according to the present invention showing the hammer at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle.

FIG. 15 is a cross section side view of the hammer of FIG. 14 at the beginning the hammer lifting stroke.

FIG. 16 is a cross section side view of the hammer of FIG. 14 shown at a position during the lifting stroke of the ram.

FIG. 17 is a cross section side view of the hammer of FIG. 14 shown at the top of its predetermined height and the beginning of the falling stroke of the ram.

FIG. 18 is a cross section side view of the hammer of FIG. 14 shown during the falling stroke of the ram.

FIG. 19 is a cross section side view of the hammer of FIG. 14 shown at the end of the falling stroke, having made impact with the pile or other driven object, at which point, the hammer is returned to the configuration of FIG. 8, in equilibrium, at rest and ready to begin another cycle.

FIG. 20 is a cross section side view of another embodiment hydraulic hammer of FIG. 14, in which a lid seals the receptacle attached beneath the piston reciprocates within a well below the otherwise normal floor of the piston cylinder to reduce the weight of fluid that reciprocates, showing the hammer at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle.

FIG. 21 is a cross section side view of FIG. 14 showing an alternative embodiment of the hydraulic hammer of FIG. 1 or FIG. 14 in which a cylinder sleeve 17 forming a piston cylinder is only loosely seated in a bore in the ram and the space between these elements is filled with a fluid such as oil a first embodiment of a hydraulic hammer (hammer) according to the present invention having a reciprocating shuttle member inside a hollow piston rod and showing the hammer at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle.

FIG. 22 is a cross section side view of an alterative embodiment of the hammer having a reciprocating shuttle member inside a hollow piston rod as shown in FIG. 1 and the reciprocating receptacle resembling a bucket suspended below the piston and reciprocating with in a well below the otherwise normal floor of the piston cylinder as shown in FIG. 14, showing the hammer at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a hydraulic hammer 10 (“hammer” 10), in an embodiment illustrated in FIGS. 1-7 which is a low headroom hammer, is mounted on a frame or saddle 12, which is preferably a spherical bearing connection and manifold, resting on a suitable supporting surface frame 15 above the pile 14 that is to be driven, or other suitable object to be driven, as the case may be. A hallmark of the hammer 10 is that the piston cyclinder 24 is formed wholly inside the ram 16, with only a cylinder head 48 projecting above the top surface of the ram 16, which allows the hammer 10 to be a low-headroom hammer for any given capacity of the hammer 10. The hammer 10 includes an “outer casing of the actuator” 16, that is a ram 16, which may be cylindrical or other desired cross section shape and that may include an inwardly tapered reduced neck portion 18, terminating in a reduced size impact or bottom portion 20 having a face 22 for striking the top surface of the pile 14. The face 22 may be flat, or have a convex dished shape. The hammer 10 may employ a conventional external frame (not shown), which is connected to the support frame 15 and which is principally cylindrical and encloses the vertical portion of the hydraulic hammer 10, with suitable guide rails to insure that the ram portion falls and rises along a desired straight path and may also include a suitable striker member (not shown) interposed between the ram 16 and the pile 13 to cushion the blow and prevent damage to the top of the pile 13.

Still referring to FIG. 1, the ram 16 is shown in a second position, that is, a striking position and is show FIG. 1 at the end of the striking position, that is, without significant pressure in the hammer 10. A piston cylinder 24, having a bottom wall 25 connected to a cylindrical side wall 27, is formed inside the ram 16. The top of the piston cylinder 24 is sealed by a cylinder head 48. The piston cylinder 24 may be formed integrally into the ram 16 or preferably consists of a sleeve 17 having a connected bottom wall 25 that is inserted into a cavity 19 in the ram 16 to form the piston cylinder 24 and may be sealed by press-fitting or the like, permitting the use of a sleeve 17 and connected bottom wall 25 of a different material that the ram 16 for longer life, more accurate machining, replacement and the like. In an alternative embodiment discussed in detail below, the sleeve 17 and connected bottom wall 25 assembly is suspended within the cavity 19 in the ram 16 with an annular space between these two members, which may be partially filled with oil or other fluid. The piston cylinder 24 is a double-acting cylinder with an accumulator. Enclosed within the piston cylinder 24 is a piston 26 that is connected to a lower end 38 of a hollow piston rod cavity 28. The upper end 23 of the hollow piston rod, which is preferably tubular, is fixed to an upper portion of the frame 12, so that the hollow piston rod 28 does not reciprocate. The piston 26 is sealed against the piston cylinder 24 by suitable piston ring seals to prevent the flow of fluids around the circumference of the piston 26, i.e. to prevent bypass or blow-by of fluids. Inside the hollow piston rod 28 is a freely moving shuttle member 30 that reciprocates in response to changes in gas pressure below it and liquid fluid pressure above it, with freedom to move constrained only the friction of its seals against the hollow piston rod 28. The shuttle member 30 is a small solid cylindrical member that is preferably made of steel, brass or the like and, in a typically sized hammer, is about 15 cm (6 in.) long and about 5.5-7.75 cm (2.5-3 in.) in diameter and weighs about 14-16 kilograms (30-35 pounds), depending on the size of a particular hammer 10 and its desired stroke length, etc. The shuttle member 30 fits into the longitudinal cylindrical cavity of the hollow piston rod 28, i.e., the cavity 40 (see especially FIG. 7). The shuttle member 30, which operates as a hydraulic accumulator, i.e., to store energy and reduce system shock, is fitted with appropriate seals to block the flow of fluids past it in either direction. The shuttle member 30 is free to float between an upper stop member 32 that is adjacent to the top end 34 of the piston rod 28 and a lower stop member 36, located adjacent to the lower end 38 of the piston rod 28. The upper stop member 32 and the lower stop member are preferably rings set into mating grooves in the inner surface of the hollow piston rod 28 and serve to constrain the reciprocal movements of the shuttle member 30. In FIG. 1, the shuttle member 30 is shown in its highest position, creating the lowest gas pressure of the cycle of lifting and falling and at its lowest position in FIG. 6, creating the highest gas pressure of the cycle of lifting and falling.

Still referring to FIG. 1, the piston 26 is fixed to the lower end 38 of the piston rod 28 and these members are always stationary. It is the ram 16 that moves up to a first or raised position (shown at its maximum height in FIG. 4) and down relative to the piston 26 and piston rod 28, that is down to its second or lowest or striking position in which the ram 16 strikes the top of the pile 14 (as first shown in FIG. 1). The cylinder reciprocates up and down relative to the piston 26. The piston cylinder 24 and the ram 16 that encloses and carries the piston cylinder 24 reciprocates by sliding up or down along the piston 26. This is the opposite of an ordinary internal combustion engine or a pump in which the engine block is stationary and the piston reciprocates inside a stationary cylinder and it is opposite of every existing hydraulic ram known the inventors of the present invention. Also opposite is that the piston rod 28 is stationary and that it does not transfer any power to another part such as a crankshaft. Conceptually, the piston cylinder 24 is the ram 16, or the piston cylinder 24 is formed in the ram 16 itself, however one wishes to view the structure. In either way of visualizing the structure of the hammer 10, the piston cylinder 24 reciprocates along a stationary piston 26. The length of the lift and subsequent fall of the ram, i.e., its stroke, is about 1.1 meters (4 feet), but it can be designed to longer or shorter, as desired.

Still referring to FIG. 1, the hammer 10 includes two separate fluid chambers for permitting fluid flows that raise and lower the ram 16. The interior volume 40 of the hollow piston rod 28 below the shuttle member 30, and of the lower piston chamber 29, which is the volume of the piston cylinder 24 above the bottom wall 25 of the piston cylinder 24 and the lower surface 31 of the piston 26, both of which vary throughout a cycle, is filled with a substantially inert gas, preferably Nitrogen (to prevent Oxygen and oil from possibly forming an explosive mixture and to prevent water formation) and operating at about 1,725 kPa (250 psi) in a closed system in which the top end is defined by the shuttle member 30, which is fitted with suitable seals to minimize leakage of the gas past it. This gas is indicated by the numeral 41, which designates a variable volume cavity 41, and is shown by stippling, with the volume of the varying volume cavity 41 varying during the cycles shown by the stippled area in the drawings, i.e, the greatest volume is at the lowest point or striking point of the ram 16, e.g., FIG. 1, and the smallest volume at the top of the stroke, or highest point of the ram 16, e.g., FIG. 4, that is, when the piston 26 is closest to the bottom wall 26 of the piston cylinder. The variable volume 41 is formed by the lower piston chamber 29 and the hollow piston rod cavity 28 up to the lower surface of said shuttle member 30, with the lower piston chamber 29 and the said hollow piston rod cavity 28 being in fluid communication with each other. These observations apply to all embodiments in this paper. Alternatively, in all embodiments, the working fluid may be water, which may be any water locally available, including salt water. The variable volume of the lower piston chamber 29 and the cavity in the hollow piston rod 28 up to the lower surface 66 of the shuttle member 30 combine to form a single sealed chamber, whose volume changes as the position of the ram 16 changes within the cylinder. Gas is added to this closed system only to maintain the desired pressure in the system. The enclosed volume of the system increases and deceases as the shuttle member 30 moves up and down inside the hollow piston rod 28 and as the lower piston chamber 29 moves up and down. The lower piston chamber 29 and the portion of the cavity of the hollow piston rod 28 below a lower surface 66 of said shuttle member 30 together form the sealed cavity that is filled with a substantially inert gas under pressure, e.g. Nitrogen.

Still referring to FIG. 1, a hydraulic fluid conduit tube 42 is concentric with and larger in diameter than the hollow piston rod 28, as best seen in FIG. 7, and is larger in diameter than the hollow piston rod 28 and is open to the top surface 44 of the piston 26 throughout the area of the cross section of the hydraulic fluid conduit tube 42 that is outside the cross section area of the hollow piston rod 28, that is, in the tube passageway 46. The hollow piston rod 28, the hydraulic fluid conduit tube 42 and the variable cylinder volume above the top surface 44 of the piston 28 are sealed by a top wall 48, that is, a cylinder head 48. The passageway 46 opens into the larger diameter cylinder volume 50 above the top surface of the piston 28. The hydraulic fluid conduit tube 42 is connected to a high pressure line 52 that is connected to a supply of hydraulic fluid pressurized by a high pressure pump 54. A pressure relief line 56 is connected to a pressure relief tank 58 at its distal end 60 and to the hollow piston rod 28 at its proximal end 62. The shuttle member 30 seals the hydraulic fluid from the gas, with the hydraulic fluids always contained above the top surface 64 of the shuttle member 30 and the gas always contained below the bottom surface 66 of the shuttle member 30. A directional valve 68 allows (open) or disallows (closed) the flow of hydraulic fluid from the high pressure hydraulic fluid line 52 to the pressure relief line 56 and thereby controlling whether or not high pressure hydraulic fluid flows into the volume space 50 above the top surface 44 of the piston 26. The flow of high-pressure hydraulic fluid into the upper piston chamber 50, exerting a downward force on the top surface 44 of the piston 28, and an upward force on the cylinder head 48. Since the piston cannot move, the increasing volume of high pressure hydraulic fluid in the variable space 50 requires that the cylinder head 48 and the attached ram 16 must be lifted up.

Still referring to FIG. 1, the upper piston chamber 50, at its maximum volume, is filled with hydraulic fluid, which may be any substantially incompressible fluid, such as petroleum oil or water, which requires less fluid that comparable prior art hydraulic hammers of similar size, resulting in more efficient hydraulic hammers. The use of reduced volumes of hydraulic fluid allows the use of a smaller capacity high pressure hydraulic fluid pump 54, reducing the energy needed to raise the ram 16, and to faster cycle times, decreasing the time needed to drive a particular pile 14, both increasing the efficiency of the overall pile driving operation.

As shown in FIG. 1, the directional valve 68 is open, so there is no pressure in the high pressure hydraulic line 52, the volume of the piston cylinder chamber 50 above the piston 26 and below the cylinder head 48 is at its minimum volume and the shuttle member 30 is at its highest point, that is, pushing against the upper stop member 32, so the gas pressure in the lower piston chamber 29 is at its lowest while the lower piston chamber 29 is at the largest volume it will reach during any portion of a cycle. The variable volume cavity 41, indicated by stippling in the relevant drawings, is at its maximum. In this configuration, the ram 16 has just struck the pile 14 and the hammer 10 is at rest and in equilibrium, ready to being the next cycle.

Referring to FIG. 2, the directional valve 68 closed, allowing the hydraulic pump 54 to pressurize the hydraulic fluid in the line 52, causing the hydraulic fluid to flow along the direction of the arrows 70 and then into the passageway 46 of the hydraulic fluid conduit tube 42 and then into the upper piston chamber 50, thereby exerting downward force on the top surface 44 of the piston 26. Since the cylinder head 48 is stationary, the resulting forces on the hydraulic fluid and its increased volume force the ram 16 to move upward, lifting the face 22 of the ram 16 above the pile 14. At the same time, the gas in the lower piston chamber 29 and the interior of the hollow piston rod 28 is being compressed, as the volume of the lower piston chamber 29 decreases, forcing the shuttle member 30 to remain pressed against the upper stop member 32. The volume of the upper piston chamber 50 and the volume of the lower piston chamber 29 change in inverse direct proportion to one another. This lifting step continues until the desired amount of lift is achieved, which may be any amount from zero, i.e., face 22 now being lifted free from the top of the pile 14, up to the maximum lift stroke allowed by the design of a particular ram 16 of particular capacity and lift, but generally being a typical lift of about 3.5 meters (4 feet), which can be controlled by opening the directional valve 68 when the desired about of lift has been achieved. This flexibility in operation allows the hammer 10 to be operated to produce any of a wide range of forces that might be desired on a particular job. Naturally, hammers 10 of different sizes will have different, appropriate, maximum lifts.

Referring to FIGS. 3, 4 the lifting step of the process of FIG. 2, that is, pumping high pressure hydraulic fluid into the passageway 46 of the hydraulic fluid conduit tube 42 and then into the upper piston chamber 50, continues and the volume of the upper piston chamber 50 increases as the volume of the hydraulic fluid in it increases and the volume of the lower piston chamber 29 continues to decrease, raising the ram 16 progressively until the desired predetermined height is reached, as shown in FIG. 3.

Referring to FIG. 4, the desired predetermined height of the ram 16 has been achieved and the ram 16 is now in a first position, and at that point, the directional valve 68 is opened, providing an alternative and un-pressurized path for the hydraulic fluid flowing from the high pressure hydraulic pump 54 and for the pressurized hydraulic fluid in the high pressure hydraulic fluid line 52, the hydraulic fluid conduit tube 42 and the upper piston chamber 50. The variable volume cavity 41 is here at its minimum volume and hence at its greatest pressure. All the hydraulic fluid in these cavities flows toward the pressure relief line 56 and the connected pressure relief tank 58, immediately releasing all the pressure in these cavities, i.e., all the pressure and the volume of hydraulic fluid that has been forcing the ram 16 into the top-of-its-stroke position shown in FIG. 3, causing the entire reversal of the flows of hydraulic fluid previously described so that the hydraulic fluid flows along the lines of the reverse direction directional arrows 72. As hydraulic fluid flows through the open directional valve 68, some of it flows through the pressure relief line 56 to the top surface 64 of the shuttle member 30 along the pressure relief directional flow arrows 74, i.e., toward the left-hand side of FIG. 4 as shown. The shuttle member 30 thereby provides a movable seal on the vessels that contain the hydraulic fluid, which becomes important in the downstroke of the ram 16. Other portions of the hydraulic fluid flow toward the right-hand side of FIG. 4 as shown, through the pressure relief line 56 to the pressure relief tank 58 as shown by the pressure relief tank flow directional arrows 76, assuring that the high pressure pump 54 cannot contribute to any hydraulic pressure in the upper piston chamber 50. Combining the stopping of applying more hydraulic fluid pressure into the upper piston chamber 50 and relieving the existing pressure via the pressure relief line 56 removes the forces that keep the ram 16 suspended above the pile 14, causing the ram 16 to fall.

Referring to FIG. 5, the ram 16 is essentially falling in free-fall and is accelerating at approximately the rate of gravitational acceleration, aided by the additional force developed by the compressed gas in the variable volume cavity 41 acting on the lower surface of the piston 26. As the ram 16 falls, the volume of the lower piston chamber 29 increases, causing the gas pressure within the sealed system of the lower piston chamber 29 and the interior of the hollow piston rod 40 to decrease. The decreased gas pressure is eventually insufficient to support the shuttle member 30 against the upper stop member 32, as shown in FIG. 4, so the shuttle member 30 falls within the hollow piston rod 40, which creates a certain amount of downward force, that is, the production of a lower pressure in the variable volume cavity 41 as the variable volume 41 expands due to the falling of the ram 16. At the same time, the hydraulic fluid is flowing along the direction of the directional arrows 74, creating downward force on the shuttle member 30, which in turn aids in drawing out hydraulic fluid from the upper piston chamber 50 faster than would occur if the only pressure relief were to provide a zero pressure pressure relief line. Because the gas in the lower piston chamber 29 and hollow piston rod 40 is sealed and the pressure on it varies only due to movement of the ram 16 relative to the piston 26 and the up or down position of the shuttle member 30 inside the hollow piston rod 40, the shuttle member 30 reciprocates up and down as the lower piston chamber increases or decreases. Since the gas is compressible, the movement of the shuttle member 30 acts like a spring, drawing further pressure off of the hydraulic fluid during the falling ram 16 step of the cycle and allowing the ram 16 to fall more nearly at the speed of gravity, since less of the gravitational drop energy is used to extract hydraulic fluid from the upper piston chamber 50 than would otherwise be the case. The movement of the shuttle member 30 and ram 16, which vary the volume of the sealed chamber 29 provides a spring action in the form of a downward force to accelerate the emptying of hydraulic fluid from the upper piston chamber 50. The magnitude of the downward force of the compressing gas on the ram 16 in the sealed chamber 29 can be controlled or modified by setting the pre-load or static equilibrium pressure int the sealed chamber 29 (and the also sealed volume of the interior of the hollow piston rod cavity 28 below the shuttle member 30, which varies throughout an up and down cycle of the ram 16, as described above) at the beginning of the lifting step of the cycle, as shown, for example, in FIG. 2.

Referring to FIG. 6, in the time between the positions of the parts shown in FIGS. 5, 6, the ram 16 has continued its fall until, as shown in FIG. 6, the shuttle member 30 being drawn downward to its lowest point where it contacts the lower stop member 36, which also marks the largest volume of the lower piston chamber 29 and the lowest resulting gas pressure within the lower piston chamber, simultaneously exerting the strongest sucking force on the hydraulic fluid that now fills the volume 40 of the hollow piston rod 28 as the shuttle member 30 falls toward the lower stop member 36. At the moment that the shuttle member 30 strikes the lower stop member 36 and the ram 16 strikes the pile 14, the hammer 10 is again at rest and equilibrium and ready for the start of the next stroke, which is initiated by closing the directional valve 68 and once again forcing hydraulic fluid into the upper piston chamber 50 to force the ram 16 to rise.

Referring to FIGS. 8-13 and 7, an alternative embodiment of the hammer 10 is shown. This embodiment is a low headroom hammer The structure of this embodiment is identical to the structure of the embodiment of FIG. 1-7 except that the shuttle member 30 and the related stops 32, 36, 38 are omitted. This change leads to a single fluid hydraulic hammer, which is again any suitable substantially incompressible fluid, such as oil, hydraulic fluid, water or the like. The steps involved in the cycling of the embodiment of FIGS. 8-13 are identical to those described above in detail relative to the embodiment of FIGS. 1-7, but the fluid flows are different due to the use of a single fluid and these are described immediately below. This embodiment requires a higher pressure hydraulic system than the embodiment shown in FIGS. 1-6 to achieve the same cycle times because a greater weight or mass of hydraulic fluid must be moved.

As shown in FIG. 8, the hammer 10 is at rest, the directional valve 68 is open and there is no pressure or fluid flow inside the hammer 10 or the high-pressure hydraulic fluid line 52 leading to it or the pressure relief line 56 leading away from it.

Referring to FIG. 9, the directional valve 68 is closed, causing the flow from the high-pressure hydraulic fluid pump 54 to flow through the line along the directional arrows 70 and into and down the tube 42 and into the upper piston chamber 50, thereby increasing the volume of the upper piston chamber 50 as it fills with fluid and thereby pulling the ram or actuator 16 up, beginning the lift portion of the cycle. At the same time, the hydraulic fluid inside the lower piston chamber 29 beneath the piston 26 is forced upwardly through the hollow piston rod cavity 28 along the path of the directional arrows 90 and through the pressure relief line 56 and to the pressure relief tank 58. The advantage of this embodiment over the embodiment of FIGS. 1-6 is that in the present embodiment, the elimination of the shuttle member reduces the complexity of the hammer 10 and the necessity of providing separate gas and liquid fluid compartments and the necessity of using a substantially inert gas to prevent possible explosions. The advantage of the embodiment of FIGS. 1-6 to this embodiment is that the embodiment of FIGS. 1-6 can be expected to have faster cycle times and achieve closer to free-fall operation because in this embodiment of FIGS. 1-7, a smaller volume of hydraulic fluid is used and there is the previously described air-spring effect that encourages the downward movement of the hammer 10 when it is dropped.

Referring to FIG. 11, at the predetermined desired height of the ram 16, the directional valve 68 is opened, relieving all the pressure on inside the hammer 10, causing the hydraulic fluid to flow upward through the tube 42 along the lines of the directional arrows 92 and into the high-pressure hydraulic fluid line 52. At the same time, pressurized hydraulic fluid from the high-pressure hydraulic pump 54 flows into the high-pressure hydraulic fluid line 52 along the path indicated by the directional arrows 94. Flows along the directional arrows 92 and 94 merge as they flow through the open directional valve 68 indicated by the merge arrow 96, causing the flow of hydraulic fluid through the pressure relief line 56 along the direction of the arrows 98 and thereby downwardly through the hollow piston rod cavity 28 and into the lower piston chamber 29, causing the volume of the lower piston chamber 29 to increase. Relieving the hydraulic fluid pressure on the top of the piston 26 in the upper piston chamber 50 allows gravity to cause the ram 10 to fall, with the pressurized hydraulic fluid flowing into the lower piston chamber 29 accelerates the fall, helping overcome frictional losses and so forth.

FIG. 12 shows the hammer 10 in the falling portion of the cycle farther down toward the pile 14, with the fluid flows shown in FIG. 11 continuing.

FIG. 13 shows the hammer 10 returned to its equilibrium position at impact, that is with no hydraulic pressure inside the hammer 10 at impact.

Referring to FIG. 14, another embodiment of the hammer is shown in a the form of a modification that can be used with the embodiment of FIGS. 1-6 or the embodiment of FIGS. 8-14. As shown in FIG. 14, a cylinder having a closed lower end is attached to the lower surface of a piston, i.e., forming a receptacle 78, which resembles a bucket, suspended beneath the piston 26 and reciprocating within a well 82 below the otherwise normal floor of the piston cylinder to reduce the volume of fluid that must be removed from the cylinder space below the piston, that is in the lower piston chamber 29, showing the hammer 10 at the completion of a downward strike on a pile or the like in equilibrium, at rest and ready to begin the lifting stroke of its cycle. The receptacle 78 is attached to the lower surface of the piston 26 by welding 80, but may be connected by any convenient means, such as threaded connection, brazing, bolting and the like. A plurality of perforations 81 are formed into an upper end of the receptacle 78 to allow the flow of hydraulic fluid from inside the receptacle 78 to outside the receptacle 78 and into the annular volume outside the receptacle 78, although there will be little flow, see below. Cut into the bottom wall 25 of the piston cylinder and into the ram 10 is a well 82, directly beneath the receptacle 78. Suitable seals in the bottom wall 25 prevent leakage of fluids around the perimeter of the receptacle 78, which reciprocates in tandem with the piston 26. This is not a low headroom embodiment, since the overall length must be greater in order to accommodate the well 82. The advantage of this embodiment is that the hydraulic fluid that is captured in the receptacle 78, which remains substantially static at all times, need not be pumped out of the lower piston chamber 29 during any portion of the cycle of lifting and falling, reducing the amount of hydraulic fluid that must be pumped, thereby reducing cycle times for a given capacity hydraulic pump 54. The disadvantages of this embodiment are that it is more complicated to build and maintain and likely cannot be made a low headroom hammer of substantial impact power.

Still referring to FIG. 14, as shown in FIGS. 14-19, this embodiment is shown without the shuttle member 30, upper stop member 32 and lower stop member 36 as previously disclosed in relation to FIGS. 8-13, but this modification can also be used with the embodiment of FIGS. 1-6. In either case, the fluids and the fluid flows are the same as described above in connection with their respective embodiments. When this modification is used with the embodiment of FIGS. 1-6, the shuttle member 30 and its upper stop member 32 and lower stop member 36 are included. When the embodiment of FIG. 14 is used with the embodiment of FIGS. 8-13, the shuttle member 30 and its upper stop member 32 and lower stop member 36 are omitted and a single working fluid is used and the fluid flows are those described above in connection with FIGS. 8-13.

Referring to FIG. 15, at the beginning of the lifting of the ram 16, the fluid flows are the same as those shown in FIG. 9 and as described in the description of FIG. 9.

Referring to FIG. 16, the lifting of the ram is continued and the fluid flows are those shown in FIG. 10 and as described in connection with FIG. 10.

Referring to FIG. 17, the ram 16 has reached its predetermined desired height and the directional valve 68 is opened, changing the fluid flows to those shown in FIG. 11 and described in connection with FIG. 11.

Referring to FIG. 18, the fluid flows shown in FIG. 17 continue, allowing the ram 16 to continue its descent.

Referring to FIG. 19, the directional valve 68 remains open, and the ram 16 has continued to fall until it strikes the pile 14 and is ready for the next cycle, initiated by closing the directional valve 68.

Referring to FIG. 20, in a modification of the embodiment of FIG. 19, a lid 84 is sealed across the top of the receptacle 78 during manufacturing, sealing a substantially inert gas such as Nitrogen inside, thereby reducing the weight of the receptacle 78 and contents, thereby reducing the reciprocating weight of the piston 26 and the receptacle 78 and its contents.

Referring to FIG. 21, there is shown an alternative embodiment of the hammer 10 in which the sleeve 17 and connected bottom wall 25 assembly is suspended within the cavity 19 in the ram 16 with an annular space 100 between these two members, including between the bottom wall 25 of the sleeve 17 and bottom wall 25 assembly and a bottom wall 102 of the cavity 19, which is partially filled with oil or other fluid. The oil fills the annular space 100 nearly to the lower surface of the cylinder head 48, but a significant gas gap is preserved so that the oil can slosh around. This arrangement makes the piston 26 and piston cylinder 24 self-aligning with the ram 16, that is, in the case that, for whatever reason, the ram 16 and piston 26 and piston cylinder 24 are urged to move along somewhat different lines, the annular space 100 and oil 88 allow for this state without damaging either the ram 16 or the piston 26 and piston cylinder 24 assembly and further, urges these members back into vertical alignment.

Referring to FIG. 22, the modification of FIG. 14, that is, including the receptacle 78 and the well 82, is shown in use with the embodiment of FIGS. 1-6, that is the embodiment utilizing the shuttle member 30 and its upper and lower stop members 34, 36. The stages of the reciprocating cycle and the fluids flows are therefore identical to those shown in FIGS. 1-6 and as described above in connection with FIGS. 1-6.

The hammer 10 has shorter cycle times than related hammers of similar striking capacity and uses less hydraulic fluid and a smaller capacity hydraulic pump. The embodiment utilizing the shuttle member 30 uses less energy than a now standard hydraulic hammer due to the use of the gas chamber actuating the moveable shuttle member, providing a spring effect to more quickly and efficiently empty the upper piston chamber of hydraulic fluid for the nearly free-fall gravity operated downstroke. The embodiment utilizing the receptacle reciprocating in the well also uses less energy than a now standard hydraulic hammer because the volume and weight of hydraulic fluid that must be exhausted from the chamber beneath the piston is reduced. The hammer 10, in, for example, the embodiment shown in FIGS. 1-6, is also a very low headroom hammer due to the advancement of forming the piston cylinder inside the ram itself

While the present invention has been described in accordance with the preferred embodiments thereof, the description is for illustration only and should not be construed as limiting the scope of the invention. Various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the following claims. 

We claim:
 1. A hydraulic hammer comprising a ram and a piston cylinder formed inside said ram, a piston seated in said cylinder, with said piston fixed to a lower end of a connecting rod with an upper end of said connecting rod fixed to a support member above said ram, hydraulic means operatively connected to said ram for moving said ram between a first position and a second position and a shuttle member seated within said hollow piston rod, said hollow piston rod having an upper end fixed to a supporting member and wherein said shuttle member is free to reciprocate within said hollow piston rod.
 2. A hydraulic hammer in accordance with claim 1 wherein said hydraulic means further comprises a source of pressurized hydraulic fluid operatively connected to an upper piston chamber created by a piston inserted into said cylinder and a cylinder head above said piston for creating hydraulic pressure inside said upper piston chamber and wherein said piston is fixed to a lower end of a piston rod and means for selectively relieving hydraulic fluid pressure inside said upper piston chamber.
 3. A hydraulic hammer in accordance with claim 3 wherein said pressure relieving means further comprises a pressure relief tank connected to said hollow pistons rod by a pressure relief line.
 4. A hydraulic hammer in accordance with claim 3 wherein said pressure relieving means further comprises a valve in a pressurized hydraulic fluid source that can be opened to allow pressurized hydraulic fluid to flow into said pressure relief line.
 5. A hydraulic hammer in accordance with claim 4 wherein said pressure relief line further comprises a passageway to an upper surface of said shuttle member inside said hollow piston rod.
 6. A hydraulic hammer in accordance with claim 3 wherein said source of pressurized hydraulic fluid operatively connected to said upper piston chamber further comprises a hydraulic fluid conduit tube larger in diameter than said hollow piston rod and concentric with said hollow piston rod.
 7. A hydraulic hammer in accordance with claim 5 further comprising a lower piston chamber and a cavity of said hollow piston rod below a lower surface of said shuttle member that further comprises a sealed cavity that is filled with a substantially inert gas under pressure.
 8. A hydraulic hammer in accordance with claim 7 wherein the volume of said lower piston chamber and said cavity of said hollow piston rod below a lower surface of said shuttle member form a variable volume cavity that varies in volume as said ram moves between said first and second positions.
 9. A hydraulic hammer in accordance with claim 2 further comprising upper and lower stop members seated inside said hollow piston rod for constraining the reciprocal movements of said shuttle member.
 10. A hydraulic hammer in accordance with claim 2 wherein said cylinder further comprises a sleeve having a bottom wall inserted into said cylinder with its bottom wall in contact with a bottom wall of said cylinder.
 11. A hydraulic hammer comprising; a. a ram; b. a cylinder formed inside said ram and sealed at its lower end by a bottom wall and sealed at its upper end by a cylinder head; c. a piston seated in said cylinder and dividing said cylinder into an upper piston chamber and a lower piston chamber; d. a hollow piston rod having an upper end fixed to a supporting member and a lower end fixed to said piston; and e. a shuttle member seated within said hollow piston rod, said hollow piston rod having an upper end fixed to a supporting member said shuttle member reciprocates freely within said hollow piston rod, moving up and down in response to changes in fluid pressure above and below said shuttle member.
 12. A hydraulic hammer in accordance with claim 11 further comprising means for supplying hydraulic fluid under pressure to said upper piston chamber.
 13. A hydraulic hammer in accordance with claim 11 further comprising a directional valve for releasing hydraulic pressure from said upper piston chamber.
 14. A hydraulic hammer in accordance with claim 13 further comprising means for applying a force to a lower surface of said piston for accelerating the relief of pressure from the hydraulic fluid in said upper piston chamber and thereby accelerating the fall of said ram.
 15. A hydraulic hammer in accordance with claim 14 wherein said force applying means further comprises said shuttle member.
 16. A hydraulic hammer in accordance with claim 15 further comprising a sealed chamber filled with gas under pressure, with said sealed chamber comprising said lower piston chamber and a cavity in said hollow piston rod up to a lower surface of said shuttle member, with said lower piston chamber and said cavity in said hollow piston rod being in fluid communication with each other.
 17. A hydraulic hammer in accordance with claim 16 wherein said gas under pressure when acted upon by a varying volume of said variable volume cavity during movements of said ram and said shuttle member provides a spring action expansion force to said lower surface of said piston to accelerate the emptying of hydraulic fluid from said upper piston chamber.
 18. A hydraulic hammer comprising; a. a ram; b. a cylinder formed inside said ram and sealed at its lower end and at its upper end; c. a piston seated in said cylinder and dividing said cylinder into an upper piston chamber and a lower piston chamber; d. a hollow piston rod having an upper end fixed to a supporting member and a lower end fixed to said piston; e. a shuttle member seated within said hollow piston rod, said hollow piston rod having an upper end fixed to a supporting member said shuttle member reciprocates freely within said hollow piston rod, moving up and down in response to changes in fluid pressure above and below said shuttle member; and f. means for applying hydraulic fluid pressure to said upper piston chamber for raising said ram and means for relieving said hydraulic fluid pressure in said upper piston cylinder for allowing said ram to fall and means for introducing hydraulic fluid into a lower piston chamber as said ram falls for accelerating the falling of said ram.
 19. A hydraulic hammer in accordance with claim 18 further comprising a receptacle attached to a lower surface of said piston and depending therefrom and a well beneath said receptacle formed in said ram whereby the volume of hydraulic fluid to be pumped is reduced.
 20. A hydraulic hammer in accordance with claim 19 further comprising means for supplying hydraulic fluid under pressure to said upper piston cylinder and means for relieving the pressure on the hydraulic fluid and for emptying the hydraulic fluid from said upper piston chamber and means for applying a downward acceleration force on said ram, said accelerating means further comprising means for controlling the magnitude of said downward acceleration force. 